This leafy green is high in vitamin K and also contains calcium and magnesium – a combo that may help slow the breakdown of bone that occurs as you get older – as well as folate, a B vitamin that helps prevent birth defects. And it packs just 7 calories per cup raw!

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PARMESAN CHEESE strengthens bones

Calcium is key for preventing osteoporosis (especially in your 20s). Yogurt and nonfat milk help, but who wants them three times a day? Work Parmesan cheese into your diet; its 340 mg of calcium per ounce – compared to about 200 mg in cheddar or Swiss – goes a long way toward your 1000 mg/day quota. (FInd the calcium supplement that works with your diet at GNC Live Well.)

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APPLES boost immunity

Smart and sweet, apples are rich in quercetin, an antioxidant that can bolster your body's disease-fighting abilities. In one study from Appalachian State University, just 5 percent of people who ate more quercetin came down with a respiratory infection over a two-week period, compared to 45 percent of those who didn't.

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LENTILS build your iron stores

Low-calorie lentils pack about 30 percent of your daily iron per cup cooked. About 12 percent of young women have low iron stores – at the extreme, that leads to anemia. But one study found that even women who were iron deficient (not anemic) had poorer performances on skill tests than those with normal levels.

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BROCCOLI fights wrinkles

"A cup of broccoli has 100 percent of your vitamin C—crucial for production of collagen, which gives skin elasticity,” says Tammy Lakatos Shames, R.D. It's also rich in beta-carotene, which the body converts to vitamin A. This vitamin assists in cell turnover, so old skin cells are replaced with fresh (read: younger-looking) ones.

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POTATOES pack healthy carbs

Potatoes contain a fat-fighting compound called resistant starch that can help keep weight in check. One medium spud with the skin will run you just around 100 calories, and with more potassium than bananas, potatoes also help fight heart disease by keeping blood pressure low.

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SPINACH is dense with key nutrients

This leafy green is high in vitamin K and also contains calcium and magnesium – a combo that may help slow the breakdown of bone that occurs as you get older – as well as folate, a B vitamin that helps prevent birth defects. And it packs just 7 calories per cup raw!

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DARK CHOCOLATE stops stress and fights disease

European researchers found that people who ate an ounce and a half of dark chocolate – about 200 calories worth—every day for two weeks produced less of the stress hormone cortisol and reported feeling less frazzled. Cortisol causes a temporary rise in blood pressure; consistently high levels up your risk for depression, obesity, heart disease and more.

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MUSHROOMS deliver cancer-fighting antioxidants

One study showed that women who ate just one third of an ounce of raw mushrooms a day (that's about one button mushroom) had a 64 percent reduction in breast cancer risk. Other research suggests that mushrooms reduce the effects of aromatase, a protein that helps produce estrogen – a major factor in some breast cancers.

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SARDINES fight heart disease

These pungent little fish are good sources of omega-3 acids, which decrease inflammation that can lead to blocked arteries. They also prevent blood clots that can cause heart attacks and strokes, and keep blood vessels smooth and supple. Three ounces of sardines have about 1.3 grams of omega-3s (you need about 1 gram a day).

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AVOCADOS help flatten your belly

Avocados are high in monounsaturated fat, which has been shown to help you drop weight, including from your troublesome middle. In one study, people who got the most monos (about 23 percent of their daily calories) had about 5 pounds less belly fat than those who ate a high-carb, lower-fat diet.

Whole-grain pasta is loaded with B vitamins, which help your body convert food into energy. And unlike processed grain products that lack fiber, whole grains are more filling than their refined counterparts. In other words, you'll feel satisfied with fewer calories. See sources.